Poly(arylene ether) copolymers are a class of thermoplastics known for excellent water resistance, dimensional stability, and inherent flame retardancy, as well as outstanding dielectric properties over wide frequency and temperature ranges. Properties such as ductility, stiffness, chemical resistance, and heat resistance can be tailored by reacting thermosetting poly(arylene ether) copolymers with various crosslinking agents in order to meet requirements of a wide variety of end uses, for example, fluid engineering parts, electrical enclosures, automotive parts, and insulation for wire and cable. In particular, poly(arylene ether) copolymers have been used in thermoset compositions for electronics applications, where they provide improved toughness and dielectric properties, among other benefits.
Thermosetting poly(arylene ether) copolymers are telechelic, in that they are endcapped with reactive groups such as vinyl. Thermosetting poly(arylene ether) copolymers are often therefore referred to as “capped”. Methods for the manufacture of capped poly(arylene ether) copolymers have been described, including methods to increase the flame retardancy by adding phosphorus containing compounds to curable compositions. However, while suitable for their intended purposes, there nonetheless remains a need for capped poly(arylene ether) copolymers that directly incorporate phosphorous into the copolymer. It would be an additional advantage if the phosphorous containing capped poly(arylene ether) copolymers could be prepared using processes that could be readily incorporated into known methods.